Independent-learning super-curriculum projects: reading, research and ideas shared by Perse students

The genetics of autosomal recessive conditions

We inherit traits (physical characteristics) or conditions (diseases or disorders) from our parents. This happens through the DNA in our genes, which are found on the chromosomes in all our cells.

Autosomal traits or conditions are passed down through the 22 non-sex chromosomes, and these are the subject of this investigation. However, some other traits or conditions are passed down through the sex chromosomes, and these will be mentioned in the final section.

A gene is made up of two different alleles – one dominant (or expressed) and one recessive (or masked), and we inherit one allele from each of our parents. Through the genetic studies of Mendel we know how these work. A very useful diagram for this is the Punnett square (see below) – the dominant allele is given an upper-case letter (e.g. R0 and the recessive allele is given a lower-case letter (e.g. r).